The present invention relates to dynamoelectric machines, and, more particularly, to electrical power generators including a rotor and a stator in which the stator includes a plurality of end windings.
A dynamoelectric machine, such as turbine-driven electrical power generator, includes a rotor and a stator surrounding the rotor. The stator includes a plurality of windings arranged in a main portion adjacent the rotor and terminating in a plurality of inner and outer end windings extending outwardly from the main portion. These inner and outer end windings are also commonly referred to as top and bottom end windings, respectively. Electrical power is generated as the rotor rotates within the stator and electrical current flows through the windings.
During operation of the electrical power generator, the end windings extending outwardly from the main portion are typically subjected to severe vibrations and stresses. Additionally, the electromagnetic forces associated with the generation of electrical power, arising especially if an abnormal short-circuit or fault occurs, may cause structural deformation of the end windings.
Therefore, at least one support ring is typically positioned adjacent the end windings to secure the end windings and prevent their deformation, which could result in an end winding contacting the rotor. The use of such support rings is disclosed, for example, in U.S. Pat. No. 6,225,726 to Rowe et al. and U.S. Pat. No. 6,054,792 to Rowe et al., each of which is assigned to the assignee of the present invention.
U.S. Pat. No. 5,140,740 to Weigelt discloses a pad between the support ring and an end winding. Such pads, for example, can be made of Dacron. Over time, however, such padding is prone to deformation and insulation creep, resulting in a loosening of the fit between the support ring and end windings. Additionally, after prolonged operation of the electrical generator, there may be shifts in the alignment of the inner end winding and support ring, causing the pad to fit less securely between the inner winding and support ring, and thereby further loosening the fit between the support ring and end winding.
As a result, the support ring less effectively secures the inner end winding. Accordingly, there is a greater chance that the support ring will not prevent vibration or deformation of the inner winding as initially intended. Moreover, loosely held pads can slide against the insulation that typically surrounds the surface of the end windings, thereby wearing away the insulation as the end windings vibrate during operation of the electrical power generator.
With the foregoing background in mind, it is therefore an object of the present invention to provide more effective support for the inner end windings of a dynamoelectric machine.
This and other objects, features, and advantages in accordance with the present invention are provided by a dynamoelectric machine comprising an end winding support assembly for providing an adjustable separation bias between at least one support ring and adjacent end windings. The dynamoelectric machine includes a rotor and a stator surrounding the rotor, the stator comprising a plurality of windings arranged in a main portion adjacent the rotor and terminating in a plurality of inner and outer windings extending outwardly from the main portion. The end winding support assembly comprises at least one support ring and a respective adjustable bias member between the support ring and each adjacent end winding. Accordingly, the support ring supports the plurality of end windings, and each adjustable bias member provides an adjustable separation bias between the support ring and adjacent end winding.
The support ring may have a plurality of passageways therein, and each adjustable bias member further may comprise a shaft received in a respective passageway and extendable outwardly therefrom. Each shaft may have an enlarged diameter medial portion, and each adjustable bias member may further comprise at least one washer, the washer being on the shaft and adjacent the enlarged diameter medial portion thereof. The at least one washer may comprise a compressible washer. More particularly, the compressible washer may comprise a spring washer.
Each passageway further may comprise a threaded end portion opposite a respective end winding, and each adjustable bias member further may comprise a threaded fastener received in the threaded end portion to adjustably engage the shaft. Additionally, each passageway may further comprise a series of non-threaded portions adjacent the threaded portion and having progressively increasing diameters.
A pair of adjacent non-threaded portions may define a shoulder for restricting movement of the enlarged diameter medial portion of the shaft. An outermost non-threaded portion may define a recess for receiving therein at least one washer on the shaft. Each adjustable bias member may further comprise a pusher plate connected to an adjacent portion of the end winding.
An additional aspect of the invention pertains to a method of supporting a plurality of inner end windings of a stator in a dynamoelectric machine. The method may include providing at least one support ring for the plurality of inner end windings and positioning a respective adjustable bias member between the at least one support ring and each adjacent inner end winding to thereby provide an adjustable separation bias therebetween. Each adjustable bias member may comprise a compressible member. The method may also comprise forming a plurality of passageways in the at least one support ring, and providing a shaft in each respective passageway of the at least one support ring so that the shaft is extendable outwardly therefrom.